The physical scattering region satisfies [1]} the following equations:
\(s_{12} > 0, ~~ s_{12} \ge s_{34}, ~~ s_{45}\le s_{12} - s_{34}, ~~ s_{23} > s_{12}-s_{45},~~ s_{51}^- \le s_{51} \le s_{51}^+ , ~~ ({\text{tr}_5})^2 < 0\,,\) 
